In a Cardiff recording studio the size of a shoebox, John Barrowman is standing with a pair of headphones clamped to his ears, his eyes tight shut. His entire face appears to be in considerable pain, but he is in fact closer to rapture. Three hours into a long day's recording for his forthcoming album, Another Side, and he is by now fully immersed in Elton John's "Your Song", a personal favourite that he has nevertheless chosen to interpret in a manner more redolent of Ewan McGregor's version in the 2001 film Moulin Rouge! The reason he is doing the song this way is because Barrowman is to musicals what, well, what Elton is to tantrums. Consequently, he is over-enunciating every syllable and kicking any subtlety into touch.
"I will not bastardise my musicality for anything," he says in sort-of explanation a quarter of an hour later, during an unofficial tea break (his producer twiddling his thumbs back in his booth). We are sat in the studio's lobby area with a bottle of water each, and Barrowman, dressed down in cotton and denim, his blue eyes burning beneath chestnut-coloured hair, makes for voluble company. Even when talking one-on-one, his voice cannot help but boom with the theatricality of one used to reaching people all the way up in the gods. He makes unswerving eye contact, too, his lids seemingly untroubled by a requirement to blink. "I can sing the high notes and the low, and so I do just that – always," he continues. "Of course, Ewan rather shouted his way out of the song. I, on the other hand, sing it proud."
Cardiff has become the performer's base of late. He is here filming the second series of the hugely popular Doctor Who spin-off, Torchwood, which is due on BBC1 in early 2008, and the long days of filming often stretch into the night and most weekends. Much like Doctor Who, Torchwood represents the acceptable face of geekdom, a TV show in which sci-fi, and all its associated gubbins, is served up as so much knowing nonsense that, mercifully, grabs every chance it gets to ramp up the attendant irony. This is thanks not only to Barrowman's performance, but also its creator, Russell T Davies, a man who rarely removes tongue from cheek. Torchwood has already inspired a legion of fans, many of whom, Google confirms, take it all terribly seriously and set up websites in its honour. "The last time we saw Jack [Harkness, Barrowman's character] he was alone," says one fan posting, "the only survivor of the Dalek invasion of Satellite 5. How did he get off the space station?" The question has so far prompted 20 responses. To read them rather wearies the soul, but it is this very slavish devotion that is fast turning Barrowman into the kind of icon future fan conventions will welcome forever more.
Whenever he has a spare moment, he chooses not to relax but instead to come here to the studio to put the finishing touches to what will be his first official album release. His voice has been on record before, mostly soundtracks to the Broadway and West End musicals he has appeared in, but Another Side is the first to, if you like, carry his name above the title. It's an inevitable, and highly calculated, cash-in on his soaring popularity, and features cover versions of some of his favourite songs – Bryan Adams' "Heaven", Cyndi Lauper's "Time After Time", Chicago's "If You Leave Me Now". Hardly an exercise in credibility-building, perhaps, but then Barrowman never craved credibility in the first place.
"Look, this is not about me setting myself up as a pop star here," he says, "but simply for those people who have seen me on television and are maybe keen to discover another side of me, that's all."
For the past couple of years, John Barrowman, a stalwart of the family-friendly West End musical (he has appeared in everything from Miss Saigon to Beauty and the Beast, from Sunset Boulevard to Phantom of the Opera) has found his true métier as TV's most likeable everyman. In that time, he has been all over our television screens like a rash: as the devilish Captain Jack Harkness in both Doctor Who and Torchwood, and as a double entendre- plundering guest on Friday Night with Jonathan Ross, Never Mind The Buzzcocks and Channel 4's Friday Night Project. He has been a judge alongside Andrew Lloyd Webber on BBC1's Any Dream Will Do (in which he helped find a new Joseph to don the old Technicolor Dreamcoat), and has graced Saturday morning food shows and countless radio programmes, and is also a very public face for several prominent charities (for cancer, for dogs). If this is indeed his moment, then he's going to milk it for all it's worth.
"I entered this industry in the first place to work," he says, "and so that's precisely what I'm doing: working. Why shouldn't I? First and foremost, it's fun, and, of course, being in demand is fantastic; I love it."
He cannot, perhaps, be blamed for such voraciousness, because his success has hardly arrived overnight. Though he doesn't quite look it, Barrowman is 40. A full 16 years previously, he was plucked from relative obscurity to star alongside Andi Peters and Emma Forbes on the BBC1 Saturday morning children's TV show Live & Kicking, a Tom Cruise-lookalike whose boundless enthusiasm didn't stop him from being increasingly sidelined until eventually he left. No matter, for he swiftly refocused his sights on his first love – stage musicals.
"I'm very driven," he notes. Too true: the man's ambitious streak was so full of its own momentum that Frankie Dettori could have mounted it and won the Grand National. "Look, I'm not going to lie to you," he says, spreading his hands, palms up. "If my career had gone the way I'd planned it back when I was a teenager, then I would be a movie star sitting in my beach house in Malibu right now, not in Cardiff, but I'd be a fool to be ungrateful for what has happened to me because my life is fabulous and I really am living out all my dreams. I'm doing TV, theatre, albums. If Hollywood never does quite come calling, I'll still die happy, don't you worry about that."
And if Hollywood does call?
"Oh, I'd be there like a shot."
Barrowman was born in Glasgow in 1967, but relocated with his family to Illinois eight years later due to his father's work (in heavy machinery). One of his earliest memories is of accompanying his mother to the record shop where she worked, and standing on the counter to sing all the Top 10 hits to the customers: "I always did love an audience."
After graduating from high school, he attended a university for performing arts and, in the late 1980s, returned to the UK where the angle of his cheekbones, coupled with an innate ability to sing and dance and entertain and do jazz hands, landed him the first in a succession of West End roles. After the disappointment of Live & Kicking, he then divided his time across the Atlantic, doing whatever came his way. He appeared in the US TV sitcom Central Park West about chic, upwardly mobile Manhattanites, but that soon bombed. He very nearly got cast as Will in Will & Grace, but was deemed by producers as not quite camp enough. He even, in 2002, attempted to crack the big screen, but his leading role in Shark Attack 3: Megalodon didn't trouble Oscar voters. Occasionally, people tried to pigeonhole him, specifically as a PG-rated entertainer. But Barrowman has always bucked against any such restrictions.
He is sitting forward now, almost shouting: "I'd never let some fucking narrow-minded casting director tell me what I could and couldn't do," he bristles. To this end, he managed to impress Sam Mendes enough for the venerable theatre director to cast him in The Fix in 1998, in what was a very different role for him.
"I played a coke-sniffing, heroin-obsessed, sex-addicted politician," he says. "It was extreme stuff, and there was a scene where I had to inject drugs directly into my crotch. People would pass out in the audience, I swear they really did." He received an Olivier nomination for the role, the resulting kudos effectively ensuring that he would never be so neatly typecast again.
"Sometimes people still refer to me as a 'gay actor', though, and I hate that because it immediately hems you in. Also, it's just wrong," he stresses. "I am not a 'gay actor'; I'm an actor that happens to be gay, and for me I think it's important to show another side to the gay world. There is absolutely nothing wrong with wearing leather chaps and having your arse hanging out, but we are not all camp. I'm a guy, and I like guy things."
Asked if he is disappointed that so many other actors who are gay remain reluctant to come out (Barrowman has always been out and proud), he simply says: "It's not my job to out anyone, but I would encourage these people to come to terms with who they are and realise that they are in the 21st century. Being openly gay has not hampered my career in any way. Why should it anyone else's?"
For a modern celebrity, Barrowman is a distinct oddity. His smile is not only a permanent fixture, but also a seemingly genuine one. While many of his peers are subject to anxiety and turmoil and tabloid scandal, he appears to glide through life with unerring optimism. Here is a man, you feel, who could front infomercials for any old tat and feel privileged to do so. It's simply his natural born character, he argues, and doubtless it is. Also, he has a very settled private life, happily married to his partner of 16 years, the architect Scott Gill. And while he insists they have suffered their fair share of tragedy – the death of their dog, and the loss of respective family members to brain tumours and cancer – he adds "the good far outweighs the bad, and I cannot help but focus on that. Why wouldn't I? I meet so many people in this industry who always feel the need to complain about everything, and it makes me so angry. Why would you bother getting into this business if it's only going to make you even more miserable than you were before? I don't understand it."
He very probably doesn't have a negative bone in his body, does he? "And what's wrong with being positive and well-balanced!" he shouts, his eyes as wide as an evangelist's. It's a shame, I tell him, that his enthusiasm doesn't come bottled. He'd make a fortune selling it. Then again, perhaps it's a good thing. Britain would implode if everyone were quite so buoyant as he. He laughs riotously, and everything but his chestnut hair quakes.
And so there we have it: John Barrowman, a man, a veritable lifeforce, so very happy with his lot: overjoyed to be the lead in Torchwood, thrilled at being a TV judge, and proud of his album of cheesily impassioned Eighties' ballads, each a dollop of sunshine that affords him a pulsing, Ready Brek glow.
His producer emerges from the studio now, and taps his watch. The performer stands to leave, he says nice things in parting, and then bounds off down the corridor, whistling loudly. It is, of course, a happy tune.
'Another Side' is released by SonyBMG on 12 November